from The Century Dictionary and Cyclopedia

n. any of a fairly recent class of Hindu or Buddhist religious literature concerned with ritual acts of body and speech and mind

n. doctrine of enlightenment as the realization of the oneness of one's self and the visible world; combines elements of Hinduism and paganism including magical and mystical elements like mantras and mudras and erotic rites; especially influential in Tibet

Etymologies

Sanskrit tantram, doctrine, loom; see ten- in Indo-European roots.

(American Heritage® Dictionary of the English Language, Fourth Edition)

From Sanskrit तन्त्र (Wiktionary)

Examples

Here, since the text indicates primarily the cleansing of the everlasting continuum of the mind when it is tarnished with fleeting stains, and thus since it concerns the everlasting mental continuum, it includes the term tantra, meaning everlasting continuum, in its title.

The way she writes you might think that tantra is a solid, inescapable fact of true polyamorous living, and that every polyamorist is a spiritual yogi seeking enlightenment through the energies released and shared during intercourse, provided of course that one has taken the time to properly align one’s chakras.

Our notions of being tight, of holding tension, anger and frustration are the opposite of the notion of tantra where you find what you intend to find, give it attention and then (physically and spiritually) stretch.